My 2002 gmc wont shift and code p1870 came up it will stay im low gear
You can replace the transmission valve body as per the instruction or
install a new TCC apply valve kit. However the installation requires for
the valve body to be removed and honed out by a special tool. I
wouldn't recommend this procedure unless you have the proper tools and
the know how about the inner workings of the automatic transmissions.
#01-07-30-023B: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) - (Mar 22, 2002)
Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body)
Models: 1996 Buick Roadmaster
1996 Cadillac Fleetwood
1999-2000 Cadillac Escalade
1996-2000 Chevrolet Camaro, Corvette
1996-2000 Pontiac Firebird
1996-2000 Chevrolet and GMC Light Duty Truck Models
1996-2000 Oldsmobile Bravada
with 4L60-E Automatic Transmission (RPO M30)
Built Prior to January 15, 2000 (Julian Date 0015)
This bulletin is being revised to update VIN Breakpoint Date information
and revise the Parts Information table. Please discard Corporate
Bulletin Number 01-07-30-023A (Section 07 -- Transmission/Transaxle).
Condition: Some customers may comment on a harsh 1-2 upshift and the
Check Engine Light or Service Engine Soon indicator is illuminated.
Diagnosis: Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs.
The scan tool may show a DTC P1870 set as a history code.
A harsh 1-2 shift or DTC P1870, caused by wear in the control valve
body, may be difficult to duplicate when the transmission temperature is
below 93°C (200°F).
Cause: The condition may be due to wear in the control valve body. This
wear occurs in the bore that contains the TCC isolator and regulator
valves, and results in poor, or no, TCC apply.
Important:
• DTC P1870 is a type B code. The conditions for setting the P1870
DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive
cycle) before setting a P1870 history code.
• When the conditions for setting DTC P1870 are met (first trip), the
PCM commands maximum line pressure and harsh 1-2 shifts are the result.
• This may result in a harsh 1-2 shift with no history code if the
conditions for setting the DTC required for the second trip are not met,
on two consecutive trips (Ignition cycles, with a drive cycle).
• When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code.
• When the P1870 code is stored, the PCM will turn on the Service
Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator
Lamp (MIL).
Correction: Install a control valve body with the revised TCC regulator
and isolator valves. Refer to the Parts Information table below. These
valves are used in all transmissions produced after January 15, 2000
(Julian Date 0015), and all of the service parts currently available
through GMSPO contain revised TCC regulator and isolator valves.
Important: If all of the following conditions are true, it is not
necessary to rebuild the transmission or to replace additional
transmission components beyond the control valve body.
• Transmission operation is normal before the transmission reaches
operating temperature, or before DTC P1870 is set (no slips, flares, or
missing gears).
• The torque converter is not blue or overheated.
• The transmission fluid is not burned or has no burned odor.
• The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments).
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